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tcp_dialer.go
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tcp_dialer.go
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package transport
import (
"context"
"errors"
"fmt"
"net"
"github.com/josexy/netstackgo/bind"
)
type tcpDialer struct{}
func (d *tcpDialer) Dial(ctx context.Context, addr string) (net.Conn, error) {
if DefaultDialerOutboundOption.Interface == "" {
dialer := &net.Dialer{Timeout: DefaultDialTimeout}
return dialer.DialContext(ctx, "tcp", addr)
}
network := "tcp"
switch network {
case "tcp4", "tcp6":
return dialSingle(ctx, network, addr)
case "tcp":
return dualStackDialContext(ctx, network, addr)
default:
return nil, errors.New("network invalid")
}
}
func dialSingle(ctx context.Context, network string, addr string) (net.Conn, error) {
dialer := &net.Dialer{Timeout: DefaultDialTimeout}
host, port, err := net.SplitHostPort(addr)
if err != nil {
return nil, err
}
ip := resolveIP(host)
if !ip.IsValid() {
return nil, fmt.Errorf("can not look up host: %s", addr)
}
if err := bind.BindToDeviceForTCP(DefaultDialerOutboundOption.Interface, dialer, network, ip); err != nil {
return nil, err
}
return dialer.DialContext(ctx, network, net.JoinHostPort(ip.String(), port))
}
func dualStackDialContext(ctx context.Context, network, addr string) (net.Conn, error) {
host, _, err := net.SplitHostPort(addr)
if err != nil {
return nil, err
}
returned := make(chan struct{})
defer close(returned)
type dialResult struct {
net.Conn
error
ipv6 bool
done bool
}
results := make(chan dialResult)
var primary, fallback dialResult
startRacer := func(ctx context.Context, network, host string, ipv6 bool) {
result := dialResult{ipv6: ipv6, done: true}
defer func() {
select {
case results <- result:
case <-returned:
if result.Conn != nil {
result.Conn.Close()
}
}
}()
result.Conn, result.error = dialSingle(ctx, network, addr)
}
go startRacer(ctx, network+"4", host, false)
go startRacer(ctx, network+"6", host, true)
for res := range results {
if res.error == nil {
return res.Conn, nil
}
if !res.ipv6 {
primary = res
} else {
fallback = res
}
if primary.done && fallback.done {
return nil, primary.error
}
}
return nil, errors.New("never touched")
}